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Electronic Head-Down Display (EHDD)

Technical Information

Catalogue No: C0066
Category: Head-Down Display [HDD]
Object Type: Display Unit
Object Name: Electronic Head-Down Display (EHDD)
Part No: 79-059-01
Serial No: 012
Manufacturer: Marconi Avionics
Division: Airborne Display [ADD]
Platform(s): Tornado
Year of Manufacture: circa 1983
Dimensions: Width (mm): 170
Height (mm): 193
Depth (mm): 410
Weight (g): 8,160
Location: Rack RAA08 [Main Store]

Marconi-Elliott Avionics
Part 79-059-01
Ser 012
Code K0656


The Electronic Head Down Display (EHDD) was fitted to the pilot’s cockpit of the Air Defence Variant (ADV) of the Tornado. On the ADV the ground mapping radar display is not required, since all radar displays are basically synthetic. The pilot has the EHDD which is an extension of the Navigator’s TVTab display system. This gives the pilot full access to all data available to the Navigator and in addition provides head-down attack information and steering for interception.
The unit has three pushbuttons and a rotary switch for mode selection and a rotary Brightness control.
The EHDD uses a high brightness green monochrome Cathode Ray Tube made by Rank Brimar with a contrast enhancement filter. (It was initially specified to have an automatic brightness control operated by monitoring the brightness of top and bottom scan lines outside the general image frame. Optical sensors were employed to measure the brightness of the few scan lines but it was found to be unworkable in its form. A more conventional method of measuring the brightness by measuring the CRT cathode current was resorted to and its physical equation replicated with analogue multipliers and log amplifiers to create the desired function. Note: Courtesy of Steve Pink)
Production Units had a bezel with photosensor slots at the sides; these were always a feature of the EHDD, so the bezel on this EHDD is probably an engineering part for bench use only. The deliverable contrast enhancement filter glass was prone to damage and delamination, and kept out of harm's way until actually needed. Development units had a mode called LANCE, (seen against the right-hand knob, which is missing) and this was changed to ATK for production units.
The -01 configuration confirms this as one of the early development units; variants certainly went up to -20. This unit has Serial Number 012 so would have been built for the Tornado ADV somewhere between the first flight of the aircraft in 1979 and entry into service in 1986.

The Waveform Generator for the EHDD produces synthetic symbols by a process called a time-shared digital technique. This gives high accuracy and avoids the ‘staircase’ effect found in raster generated graphics.

The Tornado originally came in two variants; the Interdictor Strike Version (IDS) for the German, Air Force and Navy, Italian Air Force, and the Royal Air Force, and the Air Defence Variant (ADV) for the Royal Air Force only. Marconi-Elliott Avionic Systems provided a wide range of equipment for both variants.

• Digital Autopilot Flight Director System (AFDS)in conjunction with Aeritalia, Italy
• Command Stability Augmentation System (CSAS)  in conjunction with Bodenseewerk, Germany
• Quadruplex Actuator Integrated into Fairey Hydraulics power control unit
• Stores Management System (SMS) in conjunction with Selenia, Italy
• Fuel Flowmeter System in conjunction with Teldix, Germany and OMI, Italy
• TV Tabular Display System in conjunction with AEG Telefunken, Germany
• Combined Radar and Projected Map Display (CRPMD) from Ferranti
• E-Scope Display System
• Triplex Transducer Unit
• Central Suppression Unit
• Engine Control Unit

By 1980 the Enhanced E-Scope Display (EESD) was under development. This was was a digital design with a frame store, rather than the analogue design and long persistence phosphor CRT of the original E-Scope Display (ESD). The EESD part number was 79-061-xx and this version was probably fitted to the majority of Tornado IDS aircraft.

RAF IDS variants were initially designated the Tornado GR1 with two variants called the Tornado GR1A and Tornado GR1B; the Tornado F3 was yet another version.

The contract covering the development and production investment for the Royal Air Force's mid-life update (MLU) for their 229 Tornado GRl and F3 aircraft was signed in April 1989. The upgrade included the following:

• Introduction of a new avionics architecture built around a 1553 databus.
• New sensors & Displays consisting of a Forward Looking Infra-red sensor, a Pilot's Multi-Function Display with digital map, wide angle HUD, Computer Symbol Generator, Video recording System and a Computer loading System.
• New Armament Control System consisting of a Stores Management System, a Weapon Interface Unit linked to a 1553 databus within a 1760 interface.
• A Night Vision Goggle compatible cockpit and the aircraft is also equipped with Forward Looking InfraRed (FLIR)
• Terrain Reference Navigation /Terrain Following Display/Terrain Following Switching & Logic Unit /Covert RadAlt.

Ferranti won the contract for the new HUD, Active Matrix Liquid Crystal Displays (AMLCD) to replace the TV Tabs, EHDD and E-scope. To support the new avionics a new Computer Signal Generator (CSG), with several times the computing capacity of the original Tornado main computer, and using the new high level ADA progamming language was procured

The Ferranti Nite-Op jettisonable NVGs were also procured under a separate contract.

In the event the MLU project stalled. In March 1993 a new Mid-Life Upgrade (MLU) project was launched and in1994 the UK signed a contract for MLU of GR1/GR1A/GR1Bs to GR4/GR4A standard.

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